Selective etch process of a sacrificial light absorbing material (SLAM) over a dielectric material

ABSTRACT

A process of selectively etching a sacrificial light absorbing material (SLAM) over a dielectric material, such as carbon doped oxide, on a substrate using a plasma of a gas mixture in a plasma etch chamber. The gas mixture comprises a hydrofluorocarbon gas, an optional hydrogen-containing gas, an optional fluorine-rich fluorocarbon gas, a nitrogen gas, an oxygen gas, and an inert gas. The process could provide a SLAM to a dielectric material etching selectivity ratio greater than 10:1.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 60/493,824, filed Aug. 8, 2003, which is herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method of removing asacrificial light absorbing material and polymer residues that mayremain on a substrate surface and inside openings during damascenestructure preparation.

2. Description of the Related Art

Integrated circuits have evolved into complex devices that can includemillions of components (e.g., transistors, capacitors and resistors) ona single chip. The evolution of chip designs continually requires fastercircuitry and greater circuit density. The demands for greater circuitdensity necessitate a reduction in the dimensions of the integratedcircuit components.

A dual damascene process is used to create the multi-level, high densitymetal interconnections needed for advanced, high performance integratedcircuits (ICs). The initial transition to dual damascene employed coppermetal with traditional silicon dioxide dielectric. More recently, thetrend has moved toward the replacement of silicon dioxide dielectricwith new low-k dielectric materials, such as carbon doped oxide (CDO).

The adoption of dual damascene copper metallization posed manychallenges to the patterning process. Unacceptable variations insubstrate reflectivity inhibited the well-controlled patterning of lineand space on glass-like interlayer dielectric (ILD). Use ofantireflective coating materials to suppress substrate reflectivity is acommon practice in the industry. However, applying this technique todual damascene patterning for sub-0.18 micron technology faces seriouschallenges in defect elimination and post-etch feature profile control.

A new material known as a sacrificial light absorbing material (SLAM)has recently been developed as an alternative to anti-reflective coatingto address the problems mentioned above. SLAM has the light absorbingcharacteristics that suppress substrate reflectivity. It could be a dyedspin-on-glass (“SOG”) or a dyed spin-on-polymer (“SOP”) that isdeposited by spin coating onto the substrate surface. Various methods offorming a dual damascene interconnect structure using SLAM are describedin U.S. Pat. No. 6,448,185, titled “Method for Making a SemiconductorDevice That Has a Dual Damascene Interconnect”, issued Sep. 10, 2002,and U.S. Pat. No. 6,365,529, titled “Method for Patterning DualDamascene Interconnects Using a Sacrificial Light Absorbing Material”,issued Apr. 2, 2002.

The SLAM-based dual damascene processes mentioned above address defectelimination and post-etch feature profile control issues. However, theprocess requires a wet clean step to remove the remaining SLAM and etchresidue. A wet clean step in a separate process system is time consumingand is limiting in its capability to control the post-etch featureprofile. The term “etch” as recited herein is used broadly to includeany material removal processes.

Therefore, a need exists in the art for a method of dry cleaning thesacrificial light absorbing material (SLAM) residue and post-etchpolymer residue formed during the dual damascene patterning process.

SUMMARY OF THE INVENTION

The present invention generally relates to a method of dry etchingsacrificial light absorbing material (SLAM) residue and photoresistresidue formed during fabrication of devices and interconnect structuresthat use SLAM during the fabrication process.

Embodiments of the invention provide a plasma etch process forselectively etching a SLAM over a dielectric material on a substrate,which comprises etching a layer of SLAM that lies atop a dielectriclayer using a gas mixture comprising a hydrofluorocarbon gas, anoptional hydrogen-containing gas, an optional fluorine-rich fluorocarbongas, a nitrogen-containing gas, an oxygen-containing gas and an inertgas. The sacrificial light absorbing material is, for example, TESACdyed methylsiloxane polymer. The dielectric material is, for example, acarbon doped oxide with 1 to 50% atomic weight carbon content.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1A-1I illustrate schematic cross-sections of structures thatresult after different process steps of making a copper containing dualdamascene structure.

FIG. 2 is a schematic diagram of a plasma processing apparatus that maybe used to practice embodiments of the invention described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The invention is described within the context of a method of forming adual damascene structure. Although use of the invention to form a dualdamascene structure is one embodiment of the invention, those skilled inthe art will understand that the invention may find use in anyembodiment where sacrificial light absorbing material (SLAM) residue isetched. FIGS. 1A-1I illustrate cross-sectional views that showstructures that result after various processing steps to make a coppercontaining dual damascene interconnect structure. For clarity, thesefigures are not drawn to scale. A first conductive layer 101 is formedon substrate 100. The conductive layer 101 may be made from materialsconventionally used to form conductive layers for integrated circuits,such as copper, copper alloy, aluminum, aluminum alloy, polysilicon,silicide and the like. After forming the conductive layer 101 onsubstrate 100, a barrier layer 102 is formed on the conductive layer101.

Barrier layer 102 will serve to prevent an unacceptable amount ofcopper, or other metal, from diffusing into dielectric layer 103.Barrier layer 102 also acts as an etch stop layer (ESL) to preventsubsequent via and trench etch steps from exposing conductive layer 101to subsequent etching and cleaning processes. Barrier layer 102 could bemade from silicon nitride, silicon carbide or other suitable materials.Barrier layer 102 should be thick enough to perform its diffusioninhibition and etch stop functions, but not so thick that it adverselyimpacts the overall dielectric characteristics of the combined barrierlayer 102 and dielectric layer 103.

A dielectric layer 103 is then formed on top of the barrier layer 102.The dielectric layer 103 could be up-doped silicon glass (USG),fluorine-doped silicon glass (FSG), silicon dioxide,polytetrafluoroethylene (PTFE), or a carbon doped oxide (CDO) film. Forconvenience, carbon doped oxide (CDO) will be used as an example in manyoccasions below to describe the invention. Carbon doped silicon oxide(CDO) is an oxidized organo-silane material. The organo-silane compoundsare oxidized during deposition by reaction with oxygen (O₂) or oxygencontaining compounds such as nitrous oxide (N₂O) and hydrogen peroxide(H₂O₂), such that the carbon content of the film is from 1% to 50% byatomic weight, and in one specific embodiment is about 20%. The oxidizedorgano-silane layer has a dielectric content of about 3.0. Carbon,including some organo functional groups, remaining in the oxidizedorgano layer contributes to low dielectric constants and good barrierproperties providing a barrier that inhibits for example diffusion ofmoisture or metallic compounds. Examples of CDO include BLACK DIAMOND™available from Applied Materials, Inc. located in Santa Clara, Calif.,Coral™, available from Novellus Systems, located in San Jose, Calif.,and Aurora™, available from ASM International, located in Amsterdam.Details of methods of preparing the BLACK DIAMOND™ film have beendisclosed in commonly assigned U.S. patent application Ser. No.10/121,284, titled “Crosslink Cyclo-Siloxane Compound With LinearBridging Group To Form Ultra Low K Dielectric”, filed on Apr. 11, 2002,and U.S. patent application Ser. No. 10/302,393, titled “Method ForForming Ultra Low K Films Using Electron Beam”, filed on Nov. 22, 2002.Typically, the thickness of the dielectric layer is between about 2,000and about 30,000 angstroms.

After forming dielectric layer 103, a photoresist layer 130 is depositedon top of the dielectric layer to define a via formation. An optionalhard mask layer can be deposited on the dielectric layer before thephotoresist layer 130 is formed. Such a hard mask may be desirable whenusing certain types of material to form dielectric layer 103, as is wellknown to those skilled in the art. This particular embodiment does notspecify forming a hard mask layer on top of dielectric layer 103 priorto applying the photoresist.

After photoresist 130 is conventionally patterned (shown in FIG. 1B) todefine a gap 105. Via 107 is etched through dielectric layer 103 tobarrier layer 102. Different anisotropic dry dielectric etch processeswill be used to etch the dielectric layer to form via, depending on thedielectric material used. The via etch is followed by a photoresist ashand/or clean processes to produce the structure shown in FIG. 1C. Via107 may be cleaned by using a conventional hydrogen fluoride (HF) inethylene glycol based wet etch process or by a dry clean process.

After via 107 is formed through dielectric layer 103, via 107 is filledwith a sacrificial light absorbing material (“SLAM”) layer 104 (see FIG.1D). The SLAM layer 104 should have dry etch properties similar to thoseof dielectric layer 103 during trench etch. Such dry etch propertieswould enable removal of the SLAM layer when the dielectric layer isetched to form the trench. The SLAM should also have high wet etch ordry etch selectivity compared to the dielectric, such as CDO, duringpost trench etch clean. Such high etch selectivity would allow removalof SLAM residue without significant dielectric loss during post trenchetch clean. Etch selectivity of SLAM over a dielectric, such as CDO, isthe ratio of etch rate of SLAM over the etch rate of the dielectric.

SLAM layer 104 could be a dyed spin-on-glass (SOG) or a dyedspin-on-polymer (SOP) that is deposited by spin coating. An example of aSLAM material is DUO248™ made by Honeywell Electronic Materials,Sunnyvale, Calif. DUO248™ is an antireflective polymer comprised ofTESAC (9-Anthracene Carboxymethyl Triethoxysilane) and Methylsiloxane.The design of the material is described in an article, titled “AnAnthracene-Organosiloxane Spin on Antireflective Coating for KrFLithorgraphy” SPIE 28^(th) Annual Microlithography Conference, Feb. 23,2003. Typically, about 500 and about 3,000 angstroms of the material isdeposited onto the surface of the device. The spin coating processcauses the SLAM layer 104 to completely fill the via 107 uniformly. Thedyed SOG or SOP greatly reduces, or even eliminates, substratereflectivity at deep ultraviolet (DUV) wavelengths (157, 193 or 248 nm).

After filling the via 107 with SLAM, a photoresist layer 130 is appliedon top of the SLAM layer 104. The photoresist layer 130 is thenpatterned to define a trench formation (see FIG. 1E). Afterwards, trench106 is etched into the dielectric layer 103 to form the structure shownin FIG. 1F. The trench etch process should remove the SLAM layer 104 atabout the same rate that it removes the dielectric layer 103 (such as aCDO layer), or at a slightly faster rate. The trench etch process can beperformed in the same equipment that had been used to etch, and evenclean, the via 107.

The presence of the remaining portion 109 of the SLAM layer 104, at thebottom the via 107 after trench etch, helps to protect the barrier layerduring the trench etch process. Due to this, the trench etch process canbe selected to produce superior trench and via profiles without havingto consider its effect on the selectivity between the dielectric layer103 (e.g. a CDO layer) and the barrier layer 102.

After the trench 106 is etched, the remaining portion of the photoresistlayer 130 and the remaining portion 109 of the SLAM layer 104 must beremoved. If a low temperature, low pressure oxygen based ashing step isused to remove the photoresist layer 130, followed by applying a wetetch process to remove remaining residues, the ashing and clean processmay have to be repeated to adequately remove the photoresist and theSLAM residues. In addition to requiring a significant amount of time tocomplete, such a process is relatively expensive and can modify the etchprofile in an unacceptable fashion. Moreover, the oxygen used during anashing process may react with the carbon, which is contained in thedielectric layer 103, to produce carbon dioxide that is released fromthe device. Because that reaction depletes the carbon that is includedin the dielectric layer, it may cause that layer's dielectric constantto increase significantly, and render the dielectric layer susceptibleto cracking and delamination.

For these reasons, a method of employing a forming gas to remove thephotoresist layer 130 has been described in U.S. Pat. No. 6,448,185,titled “Method for Making a Semiconductor Device That Has a DualDamascene Interconnect”, issued Sep. 10, 2002. The forming gas in onespecific embodiment comprises a plasma that contains hydrogen. Such ahydrogen containing plasma comprises 4% hydrogen in nitrogen inequipment capable of performing the ashing process. Removal ofphotoresist layer 130 generates the structure shown in FIG. 1G.

Following the photoresist removal step, remaining portions 109 of theSLAM layer 104 must be removed. In U.S. Pat. No. 6,448,185, this isdescribed to be accomplished by exposing the device to a dilute HFsolution that wet etches the SLAM layer at a significantly higher ratethan it may wet etch dielectric layer 103 (greater than 10:1). Such asolution comprises a blend of ethylene glycol (or deionized water) andHF in a ratio of between about 6:1 and about 500:1. A wet etch processthat uses such a solution removes the remaining SLAM at a substantiallyfaster rate than it removes any of the CDO.

However, wet etch is performed in a separate equipment from the etchsystem. Transporting wafers and waiting for the wet etch process queuecould be time consuming. Dry etch also generally provides better processcontrol. Therefore, it's more desirable to remove the remaining SLAMusing a dry etch process to save overall process time and better controlthe process.

In addition to eliminating a wet etch step, it is also desirable to havea dry etch process that combines the photoresist ashing step with theSLAM removal step. DUV (248 nm) photoresists typically consist ofterpolymers or copolymer of polyhydroxystyrene (PHS) of varying ratiosof copolymers and monomeric inhibitors. An example of DUV resist isApex-E® by Shipley, located in Marlborough, Mass. Since SLAM, such asDUO248™ is also a polymer, the etch process developed to etch SLAMshould also be able to etch DUV photoresist.

This invention is a highly selective plasma etch process of SLAM overthe dielectric material (such as CDO). The plasma process utilizes amixture of hydrofluorocarbon (HFC), fluorocarbon (optional), oxygen,nitrogen and inert gases to achieve higher than 5:1 selectivity,preferably higher than 10:1, and at an etch rate greater than 200angstrom per minute, preferably greater than 500 angstrom per minute.The preference of greater than 10:1 etch selectivity allows the removalof SLAM without significant loss of CDO. The etch rate also needs to behigh enough (>500 angstrom per minute) to make the process useful inmanufacturing integrated circuits.

The dry etch (or clean) process may be practiced, for example, in a dualfrequency capacitive plasma source reactor. The dual frequencycapacitive plasma source reactor may be included in a processing systemsuch as the CENTURA® semiconductor wafer processing system commerciallyavailable from Applied Materials, Inc. of Santa Clara, Calif. Thereactor and the specific SLAM removal processes performed in the reactorare discussed in detail below.

Following removal of the remaining portion 109 of the SLAM layer 104,trench 106 and via 107 are filled with second conductive layer 105. Likeconductive layer 101, conductive layer 105 for example comprises copper,and is formed using, for example, a conventional copper electroplatingprocess. When an excess amount of the material used to make layer 105 isformed on the surface of dielectric layer 103, one or morechemical-mechanical polishing (CMP) steps may be applied to remove theexcess material and to planarize the surface of layer 105. When anelectroplating process is used to form conductive layer 105 from copper,that CMP step (or steps) removes both the excess copper and theunderlying barrier layer. FIG. 1I shows the structure that results afterfilling the trench 106 and the via 107 with a conductive material, thenapplying a CMP step to remove excess material from the surface of layer103 to produce conductive layer 105. Although the embodiment shown inFIG. 1I shows only one dielectric layer and two conductive layers, theprocess described above may be repeated to form additional conductiveand dielectric layers until the desired integrated circuit interconnectstructure is produced.

In one embodiment of the invention, the reactor used to remove the SLAMis adapted for processing 300 mm wafers, operates in broad ranges of theprocess parameters and etchant chemistries, may use an endpointdetection system, and has in-situ self-cleaning capabilities. In oneembodiment, the reactor uses a VHF (very high frequency) plasma sourceto produce a high density plasma, a 13.56 MHz wafer bias source and aplasma magnetizing solenoid, such that the reactor provides independentcontrol of ion energy, plasma density and uniformity, and wafertemperature. A detailed description of a suitable dual frequencycapacitive plasma source reactor is provided in U.S. patent applicationSer. No. 10/192,271, filed Jul. 9, 2002 which is commonly assigned toApplied Materials, Inc., and is herein incorporated by reference in itsentirety.

FIG. 2 depicts a schematic, cross-sectional diagram of a dual frequencycapacitive plasma source reactor that may be used to practice thepresent invention. A reactor 202 comprises a process chamber 210 havinga conductive chamber wall 230 that is connected to an electrical ground234 and at least one solenoid segment 212 positioned exterior to thechamber wall 230. The chamber wall 230 comprises a ceramic liner 231that facilitates cleaning of the chamber 210. The byproducts and residueof the etch process are readily removed from the liner 231 after eachwafer is processed. The solenoid segment(s) 212 are controlled by a DCpower source 254 that is capable of producing at least 5 V. Processchamber 210 also includes a wafer support pedestal 216 that is spacedapart from a showerhead 232. The wafer support pedestal 216 comprises anelectrostatic chuck 226 for retaining a substrate 200 beneath theshowerhead 232. The showerhead 232 may comprise a plurality of gasdistribution zones such that various gases can be supplied to thechamber 210 using a specific gas distribution gradient. The showerhead232 is mounted to an upper electrode 228 that opposes the supportpedestal 216. The electrode 228 is coupled to an RF source 218.

The electrostatic chuck 226 is controlled by a DC power supply 220 andthe support pedestal 216, through a matching network 224, which iscoupled to a bias source 222. Optionally, the source 222 may be a DC orpulsed DC source. The upper electrode 228 is coupled to aradio-frequency (RF) source 218 through an impedance transformer 219(e.g., a quarter wavelength matching stub). The bias source 222 isgenerally capable of producing a RF signal having a tunable frequency of50 kHz to 13.56 MHz and a power of between 0 and 5000 Watts. The source218 is generally capable of producing a VHF RF signal having a tunablefrequency of about 100 to about 200 MHz and a power between about 0 andabout 2000 Watts. The interior of the chamber 210 is a high vacuumvessel that is coupled through a throttle valve 227 to a vacuum pump236. Those skilled in the art will understand that other forms of theplasma etch chamber may be used to practice the invention, including areactive ion etch (RIE) chamber, an electron cyclotron resonance (ECR)chamber, and the like.

In operation, a substrate 200 is placed on the support pedestal 216, thechamber interior is pumped down to a near vacuum environment, and a gas250 (e.g., argon), when ignited produces a plasma, is provided to theprocess chamber 210 from a gas panel 238 via the showerhead 232. The gas250 is ignited into a plasma 252 in the process chamber 210 by applyingthe power from the RF source 218 to the upper electrode 228 (anode). Amagnetic field is applied to the plasma 252 via the solenoid segment(s)212, and the support pedestal 216 is biased by applying the power fromthe bias source 222. During processing of the substrate 200, thepressure within the interior of the etch chamber 210 is controlled usingthe gas panel 338 and the throttle valve 227.

The temperature of the chamber wall 230 is controlled usingliquid-containing conduits (not shown) that are located in and aroundthe wall. Further, the temperature of the substrate 200 is controlled byregulating the temperature of the support pedestal 216 via a coolingplate (not shown) having channels formed therein for circulating acoolant. Additionally, a back side gas (e.g., helium (He) gas) isprovided from a gas source 248 into channels, which are formed by theback side of the substrate 200 and the grooves (not shown) in thesurface of the electrostatic chuck 226. The helium gas is used tofacilitate a heat transfer between the pedestal 216 and the substrate200. The electrostatic chuck 226 is heated by a resistive heater (notshown) within the chuck body to a steady state temperature and thehelium gas facilitates uniform heating of the substrate 200. Usingthermal control of the chuck 226, the substrate 200 is maintained at atemperature of between 10 and 500 degrees Celsius.

A controller 240 may be used to facilitate control of the chamber 210 asdescribed above. The controller 240 may be one of any form of a generalpurpose computer processor used in an industrial setting for controllingvarious chambers and sub-processors. The controller 240 comprises acentral processing unit (CPU) 244, a memory 242, and support circuits246 for the CPU 244 and coupled to the various components of the etchprocess chamber 210 to facilitate control of the etch process. Thememory 242 is coupled to the CPU 244. The memory 242, orcomputer-readable medium, may be one or more of readily available memorysuch as random access memory (RAM), read only memory (ROM), floppy disk,hard disk, or any other form of digital storage, local or remote. Thesupport circuits 246 are coupled to the; CPU 244 for supporting theprocessor in a conventional manner. These circuits include cache, powersupplies, clock circuits, input/output circuitry and subsystems, and thelike. A software routine 204, when executed by the CPU 244, causes thereactor to perform processes of the present invention and is generallystored in the memory 242. The software routine 204 may also be storedand/or executed by a second CPU (not shown) that is remotely locatedfrom the hardware being controlled by the CPU 244.

The software routine 204 is executed after the substrate 200 ispositioned on the pedestal 216. The software routine 204, when executedby the CPU 244, transforms the general purpose computer into a specificpurpose computer (controller) 240 that controls the chamber operationsuch that the etching process is performed. Although the process of thepresent invention is discussed as being implemented as a softwareroutine, some of the method steps that are disclosed therein may beperformed in hardware as well as by the software controller. As such,the invention may be implemented in software as executed upon a computersystem, in hardware as an application specific integrated circuit orother type of hardware implementation, or a combination of software andhardware.

The etching process of the present invention uses a mixture of processgases that provide high etch rate and a high etching selectivity of SLAMto dielectric. The gas mixture comprises a hydrofluorocarbon gas, suchas CHF₃, CH₂F₂, etc., an optional hydrogen-containing gas, such as H₂,NH₃, etc., an optional fluorine-rich fluorocarbon gas, such as CF₄,C₂F₆, etc., an oxygen-containing gas, such as O₂, CO, etc., anitrogen-containing gas, such as N₂, NH₃, NF₃, etc., and an inert gas.The inert gas is activated by the energized process gas to sputter andremove dissociated material loosely adhered to the surface of thesubstrate, thereby, enhancing the photoresist and SLAM etch rate. Theinert gas can comprise argon, xenon, neon, krypton, or helium.

One example of the gas mixture comprises CH₃F, H₂ (optional), CF₄(optional), O₂, N₂, and Ar. The CH₃F flow rate is between about 5 sccmto about 500 sccm. The H₂ flow rate is between about 0 sccm to about 500sccm. The CF₄ flow rate is between about 0 sccm to about 1000 sccm. TheO₂ flow rate is between about sccm to about 500 sccm. The N₂ flow rateis between about 5 sccm to about 500 sccm. The flow rate of Ar isbetween about 20 sccm and about 2000 sccm. The ratio of CH₃F flow rateto O₂ flow rate is between about 1 to about 20. The ratio of H₂ flowrate to O₂ flow rate is between 0 to about 5. The ratio of CF₄ flow rateto O₂ flow rate is between about 0 to about 5. The ratio of N₂ flow rateto O₂ flow rate is between about 1 to about 10. The ratio of Ar flowrate to O₂ flow rate is between about 1 to about 30. The bias power isbetween about 0 watts to about 1000 watts and the source power isbetween about 50 watts to about 5000 watts. The cathode temperature isbetween about −20° C. to about 80° C. and the process chamber pressureis between about 0.1 mTorr to about 1 Torr.

Plasma containing hydrofluorocarbon and/or fluorocarbon gases have beenused to break Si—O bond in the dielectric material. The etching reactionmay include,2CF₂+SiO₂−>SiF₄+COSince SLAM contains siloxane polymer, it makes sense to includehydrofluorocarbon and/or fluorocarbon gases in the gas mixture to assistin breaking the Si—O bond. The hydrogen-rich fluorocarbon gas can alsohave another function. Hydrogen-containing gas can provide hydrogen orhydrogen-containing radicals in the etching plasma that, when combinedwith nitrogen or nitrogen-containing radicals, break the Si—CH₃ bondfaster, resulting in faster etch rate and higher etch selectivity. Theoxygen gas provides oxygen radicals to react with the hydrocarboncomponents of the organic polymer of the photoresist and SLAM to formgaseous carbon compounds, such as CO, CO₂, and hydrogen compounds, suchas HF, other carbon-containing or hydrogen-containing gases, that areexhausted from the process chamber. Nitrogen-containing gas in theprocess gas has been found to help break the Si—CH₃ bond

A gas mixture containing only fluorocarbon gases (without CH₃F), CF₄ andC₄F₆, O₂, N₂, and Ar does not yield high selectivity. Increasing theratio of C₄F₆ flow rate to CF₄+C₄F₆ flow rates degrades the etchselectivity from 1.6 to 1. The studies were conducted using 200 sccm Ar,0 to 30 sccm C4F6, 5 to 50 sccm CF₄, 40 sccm O₂, 30 mTorr chamberpressure, 300 watts bias power and 400 watts source power.

The addition of the hydrogen-containing CH₃F gas helps to enhance theSLAM/CDO etch (or removal) selectivity. Table 1 shows the etchselectivity of SLAM to CDO. For example, as the ratio of CH₃F to CH₃Fand CF₄ increases from 0 to 0.9, the etch selectivity of SLAM/CDOincreases from about 1.6 to about 2.8. The studies were conducted under200 sccm Ar, 0 to 40 sccm CH₃F, 5 to 50 sccm CF₄, 40 sccm O₂, 30 mTorrchamber pressure, 300 watts bias power and 400 watts source power.

TABLE 1 SLAM/CDO etch selectivity as a function of CH₃F/(CF₄ + CH₃F).CH₃F/(CF₄ + CH₃F) SLAM/CDO selectivity 0.0 1.6 0.4 1.8 0.8 2.2 0.9 2.8

High SLAM/CDO etch selectivity, such as 13, can be achieved without theCF₄ gas. However, without the CF₄ gas, the etch uniformity for SLAM ispoor (as high as 30%) and the etch rate is low (see Table 2). Etchuniformity is defined by dividing the net value of maximum etchthickness subtracting the minimum etch thickness by 2 times the averagethickness. The studies were conducted using 200 sccm Ar, 30 to 40 sccmCH₃F, 40 sccm O₂, 20 sccm N₂, 30 mTorr chamber pressure, 300 watts biaspower and 400 watts source power.

TABLE 2 SLAM/CDO etch selectivity as a function of CH₃F flow rate. CH₃Fflow rate, sccm SLAM/CDO selectivity 30 13 40 7.5

The addition of CF₄ improves etch uniformity and etch rates for bothmaterials, but it shows little effect on SLAM/CDO etch selectivity. Asmall amount of CF₄, such as 10 sccm, can drastically improve etchuniformity and etch rate for both materials (see Table 3). The studieswere conducted using 200 sccm Ar, 40 sccm CH₃F, 0 to 10 sccm CF₄, 40sccm O₂, 20 sccm N₂, 30 mTorr chamber pressure, 300 watts bias power and400 watts source power.

TABLE 3 SLAM and CDO etch rates as a function of CF₄ flow rate. CF₄ flowrate (sccm) SLAM etch rate (Å/min) CDO etch rate (Å/min)  0  800 125 102500 385

The addition of N₂ also helps improve the SLAM/CDO etch selectivity. Byadding 20 sccm N₂ to the gas mixture, the SLAM/CDO etch selectivitydoubles. However, further increasing N₂ from 20 sccm to 40 sccm does notaffect the etch selectivity or etch rates of both materials (SLAM andCDO) (see Table 4). The studies were conducted using 200 sccm Ar, 40sccm CH₃F, 10 sccm CF₄, 40 sccm O₂, 0to 40 sccm N₂, 30 mTorr chamberpressure, 300 watts bias power and 400 watts source power.

TABLE 4 SLAM/CDO etch selectivity as a function of N₂ flow rate. N₂ flowrate, sccm SLAM/CDO selectivity  0 2.2 20 4.0 40 3.9

Bias power level affects SLAM etch rate, CDO etch rate and SLAM etchuniformity. Increasing the bias power from 200 watts to 300 wattsincreases the etch rates for SLAM and CDO, but the increase shows littleeffect on the SLAM/CDO etch selectivity (see Table 5). Bias powerincrease is found to reduce (or improve) the SLAM etch non-uniformitysignificantly. The studies were conducted using 200 sccm Ar, 40 sccmCH₃F, 10 sccm CF₄, 40 sccm O₂, 20 sccm of N₂, 30 mTorr chamber pressure,200 to 300 watts bias power and 400 watts source power.

TABLE 5 SLAM and CDO etch rates as a function of bias power. Bias power(watts) SLAM etch rate (Å/min) CDO etch rate (Å/min) 200 1600 390 3002700 680

Source power level does not affect the SLAM etch rate or CDO etch rate;however, it affects SLAM etch uniformity. Increasing the source powerfrom 400 watts to 800 watts shows no effect on etch rates for SLAM andCDO; therefore, the increase has no effect on SLAM/CDO etch selectivity.However, the 400 watt source power increase would severely degrade theSLAM etch uniformity. The studies were conducted using 200 sccm Ar, 40sccm CH₃F, 10 sccm CF₄, 40 sccm O₂, 20 sccm N₂, 30 mTorr chamberpressure, 300 watts bias power and 400 to 800 watts source power.

Temperature plays a major role in the etch process. Increasing thecathode temperature from −10° C. to 20° C. nearly doubles the SLAM/CDOetch selectivity (from 2.1 to 4.0). If the cathode temperature isincreased further to 40° C., the SLAM/CDO etch selectivity could furtherincrease to 6.7. Changing the cathode temperature can be accomplished byvarying the He backside pressure. Backside He has cooling effect andlowering the He pressure could increase the cathode temperature.Changing the cathode temperature to be in the range of −10° C. to 40° C.has little effect on the SLAM etch rate. The increase in etchselectivity is mainly cause by the decrease in CDO etch rate at highercathode temperature (see Table 6). The CDO etch reaction appears to belimited by the adsorption or desorption of reactants and/or products inthis temperature range. Since the CDO etch rate decreases from 1250Å/min to 400 Å/min linearly from −10° C. to 30° C., the reaction doesnot seem to be limited by reactants or products gas phasetransportation. Since the reaction rate change is linear, notexponential, the CDO etch reaction also does not seem to be limited byreaction. The only possible explanation is that the CDO etch in thistemperature range is limited by surface adsorption or surface desorptionof reactants and/or products. The studies were conducted using 200 sccmAr, 40 sccm CH₃F, 10 sccm CF₄, 40 sccm O₂, 20 sccm N₂, 30 mTorr chamberpressure, 300 watts bias power and 400 to 800 watts source power.

TABLE 6 CDO etch rate and SLAM/CDO etch selectivity as a function ofcathode temperature. Cathode T, (° C.) CDO etch rate (Å/min) SLAM/CDOetch selectivity −10 1250 2.1 20 680 4.0 30 400 6.8

The gas mixture used to etch SLAM can also be used to remove thephotoresist (PR), such a DUV resist is Apex-E® by Shipley. Thephotoresist ashing step can be completed in the same chamber used toetch SLAM. The recipe may comprise one single recipe or a two-steprecipe with the first step focusing on photoresist ashing. The studiesshow that the photoresist removal rate is highly affected by the Oxygen(O₂) flow rate. Increasing the O₂ flow rate from 30 sccm to 40 sccmincreases the photoresist removal rate from 1400 Å/min to 2100 Å/min.The selectivity of SLAM to photoresist is between 1.2 and 1.6 (see Table7), which shows that photoresist removal by this gas mixture is verysimilar to SLAM. This shows the possibility of combining the photoresistashing step with the SLAM etch (clean) step. The studies were conductedusing 200 sccm Ar, 40 sccm CH₃F, 10 sccm CF₄, 30 to 40 sccm O₂, 20 sccmN₂, 30 mTorr chamber pressure, 300 watts bias power and 400 watts sourcepower.

TABLE 7 PR etch rate and SLAM/CDO etch selectivity as a function of O2flow rate. O2 flow PR etch SLAM/CDO rate (sccm) rate (Å/min) etchselectivity 30 1380 1.6 40 2100 1.2

While foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof.

1. A method for selectively etching a sacrificial light absorbingmaterial over a dielectric material on a substrate, comprising:providing a substrate comprising a sacrificial light absorbing materialand a dielectric material to a process chamber; supplying to the processchamber a process gas mixture comprising a hydrofluorocarbon gas, anitrogen-containing gas, an oxygen-containing gas, an inert gas, and atleast one of a hydrogen-containing gas or a fluorine-rich fluorocarbongas; and dissociating and ionizing the process gas mixture to etch thesacrificial light absorbing material.
 2. The method of claim 1 whereinthe hydrofluorocarbon gas is CH₃F, the flow rate is between about 5 sccmto about 500 sccm and the flow ratio of the hydroflurocarbon gas to theoxygen-containing gas is between about 1 to about
 20. 3. The method ofclaim 1 wherein the hydrogen-containing gas is H₂, the flow rate is lessthan about 500 sccm and the flow ratio of the hydrogen-containing gas tothe oxygen-containing gas is less than about
 5. 4. The method of claim 1wherein the fluorine-rich fluorocarbon gas is CF₄, the flow rate is lessthan about 1000 sccm and the flow ratio of the fluorine-richfluorocarbon gas to the oxygen-containing gas is less than about
 5. 5.The method of claim 1 wherein the nitrogen-containing gas is nitrogen,the flow rate is between about 5 sccm to about 500 sccm and the flowratio of the nitrogen-containing gas to the oxygen-containing gas isbetween about 1 to about
 10. 6. The method of claim 1 wherein theoxygen-containing gas is oxygen and the flow rate is between about 5sccm to about 500 sccm.
 7. The method of claim 1 wherein the inert gasis argon, the flow rate is between about 20 sccm to about 2000 sccm andthe flow ratio of the inert gas to the oxygen-containing gas is betweenabout 1 to about
 30. 8. The method of claim 1 wherein the sacrificiallight absorbing material is 9-anthracene carboxymethyl triethoxysilane(TESAC) dyed methylsiloxane polymer.
 9. The method of claim 1 whereinthe sacrificial light absorbing material is formed atop a dielectricmaterial, where the dielectric material is a carbon doped oxide with 1to 50% atomic weight carbon content.
 10. The method of claim 1 furthercomprising: applying a bias power of less than 1000 watts.
 11. Themethod of claim 1 wherein the source power is between 50 to 5000 watts.12. The method of claim 1 wherein the cathode temperature is maintainedbetween −20° C. to 80° C.
 13. The method of claim 1 wherein the processpressure is between 1 mTorr to about 1 Torr.
 14. The method of claim 1wherein the etch selectivity of the sacrificial light absorbing materialover the dielectric material is higher than 5:1.
 15. The method of claim1 wherein the etch selectivity of the sacrificial light absorbingmaterial over the dielectric material is higher than 10:1.
 16. Themethod of claim 1 wherein the etch rate of the sacrificial lightabsorbing material is greater than 200 angstrom per minute.
 17. Themethod of claim 1 wherein the etch rate of the sacrificial lightabsorbing material is greater than 500 angstrom per minute.
 18. A methodfor selectively etching a photoresist material over a dielectricmaterial and selectively etching a sacrificial light absorbing materialover a dielectric material on a substrate, comprising: providing asubstrate comprising a photoresist material, a sacrificial lightabsorbing material, and a dielectric material; supplying to the processchamber a process gas mixture comprising a hydrofluorocarbon gas, anitrogen-containing gas, an oxygen-containing gas and an inert gas; anddissociating and ionizing the process gas mixture to remove thephotoresist material and the sacrificial light absorbing material. 19.The method of claim 18 wherein the hydrofluorocarbon gas is CH₃F, theflow rate is between about 5 sccm to about 500 sccm and the flow ratioof the hydroflurocarbon gas to the oxygen-containing gas is betweenabout 1 to about
 20. 20. The method of claim 18 wherein thenitrogen-containing gas flow rate is between about 5 sccm to about 500sccm and the flow ratio of the nitrogen gas to the oxygen-containing gasis between about 1 to about
 10. 21. The method of claim 18 wherein theoxygen-containing gas is oxygen and the flow rate is between about 5sccm to about 500 sccm.
 22. The method of claim 18 wherein the inert gasis argon, the flow rate is between about 20 sccm to about 2000 sccm andthe flow ratio of the inert gas to the oxygen-containing gas is betweenabout 1 to about
 30. 23. The method of claim 18 wherein the sacrificiallight absorbing material is 9-anthracene carboxymethyl triethoxysilane(TESAC) dyed methylsiloxane polymer.
 24. The method of claim 18 whereinthe photoresist is a deep ultraviolet (DUV) photoresist.
 25. The methodof claim 18 wherein the sacrificial light absorbing material is formedatop a dielectric material, where the dielectric material is a carbondoped oxide with 1 to 50% atomic weight carbon content.
 26. The methodof claim 18, wherein the photoresist is formed atop the sacrificiallight absorbing material.
 27. The method of claim 18 further comprising:applying a bias power of less than 1000 watts.
 28. The method of claim18 wherein the source power is between 50 to 5000 watts.
 29. The plasmaetch process of claim 18 wherein the cathode temperature is maintainedbetween −20° C. to 80° C.
 30. The method of claim 18 wherein the processpressure is between 1 mTorr to about 1 Torr.
 31. The method of claim 18wherein the etch selectivity of the sacrificial light absorbing materialover the dielectric material is higher than 5:1 and the etch selectivityof the photoresist material over the dielectric material is higher than5:1.
 32. The method of claim 18 wherein the etch selectivity of thesacrificial light absorbing material over the dielectric material ishigher than 10:1 and the etch selectivity of the photoresist materialover the dielectric material is higher than 10:1.
 33. The method ofclaim 18 wherein the process gas mixture further comprises at least oneof a hydrogen-containing gas or a fluorine-rich fluorocarbon gas. 34.The method of claim 33 wherein the hydrogen-containing gas is H₂, theflow rate is less than about 500 sccm and the flow ratio of thehydrogen-containing gas to the oxygen-containing gas is less than about5.
 35. The method of claim 33 wherein the fluorine-rich fluorocarbon gasis CF₄, the flow rate is less than about 1000 sccm and the flow ratio ofthe fluorine-rich flurocarbon gas to the oxygen-containing gas is lessthan about
 5. 36. The method of claim 18 wherein the etch rates of thesacrificial light absorbing material and the photoresist are greaterthan 200 angstrom per minute.
 37. The method of claim 36 wherein theetch rates of the sacrificial light absorbing material and thephotoresist are greater than 500 angstrom per minute.
 38. A plasma etchprocess for selectively etching a sacrificial light absorbing materialover a dielectric material on a substrate, comprising: providing asubstrate comprising a sacrificial light absorbing material and adielectric material to a process chamber; supplying to the processchamber a process gas mixture comprising a CH₃F gas flow rate betweenabout 5 sccm to about 500 sccm, a nitrogen gas flow rate between about 5sccm to about 500 sccm, an oxygen gas flow rate between about 5 sccm toabout 500 sccm, an argon gas flow rate between about 20 sccm to about2000 sccm, and at least one of hydrogen (H₂) at a gas flow rate of lessthan about 500 sccm or fluorocarbon (CF₄) at a gas flow rate of lessthan about 1000 sccm, the ratio of CH₃F flow rate to oxygen flow rate isbetween about 1 to about 20, the ratio of nitrogen flow rate to oxygenflow rate is between about 1 to about 10, and the ratio of Ar flow rateto oxygen flow rate is between about 1 to about 30; supplying theprocess chamber with a bias power of less than about 1000 watts and asource power between about 50 watts to about 5000 watts, maintaining thecathode temperature between about −20° C. to about 80° C. and chamberpressure between about 1 mTorr to about 1 Torr; and dissociating andionizing the process gas mixture to etch the sacrificial light absorbingmaterial.
 39. The method of claim 38 wherein a gas flow rate of hydrogen(H₂) or fluorocarbon (CF₄) to oxygen is less than about
 5. 40. A methodfor selectively etching a sacrificial light absorbing material over adielectric material on a substrate, comprising: providing to a processchamber a substrate comprising a dielectric material having a via formedtherein, a sacrificial light absorbing material disposed atop thedielectric material and filling the via, and a photoresist layerdisposed atop the sacrificial light absorbing material and patterned todefine a trench aligned with the via; etching the trench into thesacrificial light absorbing material and the dielectric material,wherein at least a portion of the sacrificial light absorbing materialremains deposited within the via upon completion of etching the trench;and removing the photoresist layer and the remaining portion of thesacrificial light absorbing material deposited within the via using aplasma formed from a process gas mixture comprising a hydrofluorocarbongas, a nitrogen-containing gas, an oxygen-containing gas, and an inertgas.
 41. The method of claim 40 wherein the process gas mixture furthercomprises at least one of a hydrogen-containing gas or a fluorine-richfluorocarbon gas.